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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

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HIDDEN, FOURTH AND SMALLER GLACIERS
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terminus, being, therefore, about as .wide as Nunatak Glacier or Turner Glacier within its mountain valley. Its surface was not notably crevassed and its front did not extend to the sea. Snow-capped mountains rise above it, on either side (PI. LXXIEI), and a number of small tributary glaciers descend from extensive snowfields on the slopes of the enclosing mountains; but there is no proof of the existence of any large tributaries.
In 1905 the lower five or six miles of Hidden Glacier reminded one very much of the Orange and Fourth Glaciers. The glacier surface was smooth and only slightly crevassed, and there was an almost total absence of morainic debris. On each side of the lower glacier there was a well-defined lateral moraine which in its lower portion rose in the form of an irregular ridge because of the protection which the moraine cover gave to the underlying ice. There were two medial moraines, one coming down to the front close by the southern lateral moraine, the other a few hundred yards farther north. These two medial moraines are interpreted as representing the incoming of two weaker tributaries from the south side and further as indication that the main glacier supply is either from the east or from the north, presumably the former because of the narrow belt of mountains on the north side between the Nunatak and Hidden Glaciers. The lateral moraines extended a short distance beyond the visible front of the Hidden Glacier, forming a hummocky group of ice-cored morainic hills. Between the lateral and medial moraines, even at the very front of the glacier, the surface was remarkably free from moraine, only a small amount of staining in the outermost portion discoloring the otherwise clear ice surface.
The lowest tributary to the Hidden Glacier entered it about half a mile from its front. This tributary is short and is supplied from a great snowfield that clothes the steep upper portion of its valley; but it was evidently not supplying a great amount of ice to Hidden Glacier in 1905 for its lower portion was completely covered by ablation moraine. Ablation was in rapid progress all over the lower part of the Hidden Glacier, and the snow line lay far up the glacier.
The surface slope of Hidden Glacier was very moderate, but at the front the slope increased to from 10 to 20. Here the glacier apparen&y terminated and from the visible front two fair-sized glacial streams emerged, besides several smaller ones. The smaller of the two streams came from the ice on the north side of the valley, entered a deep gorge cut in older glacial gravels, then flowed out in numerous branches over an alluvial fan which graded down to the outwash gravel plain that lay between the front of Hidden Glacier and the sea. According to the Boundary Commission map of 1895 (Fig. 12), and the map made by Gannett in 1899 (PL LXXXV, A), the stream on the north side
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FIG. 12.   THH WHOLE OF HIDDEN GIAOTHE.   EBONT SHOWN AS MAPPED BY CANADIAN BOUNDABT SURVEY IN 1890.